Field of the Invention
The present invention relates to a hydraulic pump adapted for a hydrostatic transmission (hereinafter, referred to as “HST”) including a hydraulic motor.
Related Art
As disclosed by JP 2015-055180 A, an HST including a hydraulic pump and a hydraulic motor is well-known as a transmission broadly adaptable to various working vehicles, e.g., a mower tractor. The disclosed HST includes a housing incorporating both the hydraulic pump and the hydraulic motor. In the HST, a servo unit for controlling tilt angle and direction of a movable swash plate of the hydraulic pump is detachably attached to the housing.
The above-mentioned assembly as the HST including the hydraulic pump and motor is advantageous to reduce component parts. For example, the HST does not need pipes interposed between the hydraulic pump and the hydraulic motor.
Further, the servo unit can be detached from the housing so that the HST can be provided with an actuator which does not use an expensive servomechanism to control the tilt angle and direction of the movable swash plate. The actuator is also detachable from the HST so as to be exchangeable for the servo unit.
However, in some cases, a vehicle is desired to have another typed HST in which a hydraulic pump and a hydraulic motor are separated from each other rather than those combined as an assembly. The hydraulic pump separated from the hydraulic motor is minimized advantageously to enhance a freedom in layout thereof. The hydraulic pump separated from the hydraulic motor is also desired to have either the detachable servo unit or the detachable actuator without a servomechanism, so that the servo unit and the actuator are exchangeable for each other.